Polycentridae

Leaffishes are small freshwater fishes of the Polycentridae family, from South America.

All of these fishes are highly specialized ambush predators that resemble leaves, down to the point that their swimming style resembles a drifting leaf (thus the common name leaf fish, which is shared with old world fishes of family Nandidae with a similar lifestyle); when a prey animal - such as an aquatic insect or smaller fish - comes within range, the fish attacks, swallowing the prey potentially within a quarter of a second. To aid in this lifestyle, all members of the family have large heads, cryptic colors and very large protractile mouths capable of taking prey items nearly as large as they are. These intriguing behaviors have given the family a niche in the aquarium hobby; however, none of these species are easy to maintain in aquariums, requiring very clean, soft, acidic water and copious amounts of live foods.